Posted by Hannah on .
What is the pH of a 5.06E2 M aqueous solution of sodium acetate?
I know that I would set this up the same way I did for the previous question that I posted. I am just confused on how to find the Ka. I know it is kw/kb but for what compound is what I do not know.

Chemistry(Please help) 
DrBob222,
You want to find Kb for acetate. That is Kw/Ka and Ka is for acetic acid.

Chemistry(Please help) 
Hannah,
ok thank you!

Chemistry(Please help) 
Hannah,
so for Kb

Chemistry(Please help) 
Hannah,
So for Kb I did kw/ka = 1.0e14/1.8e5 = 5.55e10 . Now I would multiply this by 5.06e6 and take the square root and then covert to pH by taking the log. Is this correct?

Chemistry(Please help) 
DrBob222,
Yes, however the number is 5.06E2 and not 6. Note, too, that a quadratic may be necessary. You will substitute 0.0506x for (acetate) in the equation and the x may (or may not) be negligible.

Chemistry(Please help) 
Hannah,
I set this up as 5.55e10 = x^2/0.0506x
After converting to pH I got 5.27 but it said that this was incorrect so maybe I do need to use a quadratic, but I am not sure how to go about this.